/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.tomcat.websocket.server;

import org.apache.tomcat.websocket.BackgroundProcess;
import org.apache.tomcat.websocket.BackgroundProcessManager;

import java.util.Comparator;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentSkipListSet;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Provides timeouts for asynchronous web socket writes. On the server side we
 * only have access to {@link javax.servlet.ServletOutputStream} and
 * {@link javax.servlet.ServletInputStream} so there is no way to set a timeout
 * for writes to the client.
 */
public class WsWriteTimeout implements BackgroundProcess {

	private final Set<WsRemoteEndpointImplServer> endpoints =
			new ConcurrentSkipListSet<WsRemoteEndpointImplServer>(new EndpointComparator());
	private final AtomicInteger count = new AtomicInteger(0);
	private int backgroundProcessCount = 0;
	private volatile int processPeriod = 1;

	@Override
	public void backgroundProcess() {
		// This method gets called once a second.
		backgroundProcessCount++;

		if (backgroundProcessCount >= processPeriod) {
			backgroundProcessCount = 0;

			long now = System.currentTimeMillis();
			Iterator<WsRemoteEndpointImplServer> iter = endpoints.iterator();
			while (iter.hasNext()) {
				WsRemoteEndpointImplServer endpoint = iter.next();
				if (endpoint.getTimeoutExpiry() < now) {
					// Background thread, not the thread that triggered the
					// write so no need to use a dispatch
					endpoint.onTimeout(false);
				} else {
					// Endpoints are ordered by timeout expiry so if this point
					// is reached there is no need to check the remaining
					// endpoints
					break;
				}
			}
		}
	}

	/**
	 * {@inheritDoc}
	 * <p>
	 * The default value is 1 which means asynchronous write timeouts are
	 * processed every 1 second.
	 */
	@Override
	public int getProcessPeriod() {
		return processPeriod;
	}

	@Override
	public void setProcessPeriod(int period) {
		this.processPeriod = period;
	}

	public void register(WsRemoteEndpointImplServer endpoint) {
		boolean result = endpoints.add(endpoint);
		if (result) {
			int newCount = count.incrementAndGet();
			if (newCount == 1) {
				BackgroundProcessManager.getInstance().register(this);
			}
		}
	}

	public void unregister(WsRemoteEndpointImplServer endpoint) {
		boolean result = endpoints.remove(endpoint);
		if (result) {
			int newCount = count.decrementAndGet();
			if (newCount == 0) {
				BackgroundProcessManager.getInstance().unregister(this);
			}
		}
	}

	/**
	 * Note: this comparator imposes orderings that are inconsistent with equals
	 */
	private static class EndpointComparator implements
			Comparator<WsRemoteEndpointImplServer> {

		@Override
		public int compare(WsRemoteEndpointImplServer o1,
		                   WsRemoteEndpointImplServer o2) {

			long t1 = o1.getTimeoutExpiry();
			long t2 = o2.getTimeoutExpiry();

			if (t1 < t2) {
				return -1;
			} else if (t1 == t2) {
				return 0;
			} else {
				return 1;
			}
		}
	}
}
